The causes of psoriasis are complex and the etiology is not yet clear. In recent years, most scholars believe that it is related to infection, metabolic disorders, genetics, immune dysfunction, and endocrine disorders. Psoriasis is not an infectious disease, but because of the skin problems of psoriasis patients, it often brings great physical and mental pain and economic burden to patients. Preliminary observation is that psoriasis is related to the following factors: 1. Infectious factors: Some people think that it is caused by viral infection, although it has been found that there are eosinophilic inclusion bodies in the nucleus of epidermal spiny cells, but so far the viral culture has not been successful. The streptococcal infection may be an important triggering factor for this disease, as acute punctate psoriasis often has acute tonsillitis or upper respiratory tract infection before the rash develops. 2, mental factors: mental trauma and emotional stress and overwork can trigger the disease or aggravate the disease. 3, genetic factors: it is believed that the disease is controlled by multiple genes and also influenced by other external factors. 4, immune dysfunction: some patients have low cellular immune function; some have increased serum IgG, IgA, IgE; some patients have anti-IgG antibodies in the serum; some people have measured anti-keratin autoantibodies in the epidermal keratin layer of patients by immunofluorescence technology. 5. Metabolic disorders: There are reports of increased serum lipids, cholesterol, globulin, sugar, uric acid, potassium, etc., and decreased folate content, but no definite conclusion can be made. There are also reports of increased polyamines and arachidonic acid in the skin lesions. 6, other: most patients relapse and aggravation in winter, remission or natural remission in summer, but seasonal regularity disappears in long-standing disease. Some women patients also aggravate around menstruation, the rash subsides during pregnancy and recurs after delivery. Chloroquine, lithium carbonate and beta-adrenergic blocking drugs can aggravate the disease.